In one known method of manufacturing a fibre reinforced metal matrix composite article, as disclosed in European patent No. EP0831154B1, a plurality of metal-coated fibres are placed in an annular groove in a metal ring and a metal ring is placed on top of the metal-coated fibres. Each of the metal-coated fibres is wound in a plane and the metal-coated fibre spirals are stacked in the annular groove in the metal ring. The metal ring is pressed predominantly axially to consolidate the assembly and to diffusion bond the metal rings and the metal-coated fibre spirals together to form an integral structure.
In a further known method of manufacturing a fibre reinforced metal matrix composite article, as disclosed in European patent application No. EP1288324A2, the arrangement described in EP0831154B1 is modified by the inclusion of metal wires in the annular groove in the metal ring with the metal-coated fibres. Each of the metal wires is wound spirally in a plane and the metal wire spirals are stacked in the annular groove in the metal ring with the metal-coated fibre spirals.
In these methods of manufacturing a fibre reinforced metal matrix composite the assembly of metal rings and metal-coated fibre spirals, or metal-coated fibre spirals and metal wire spirals, is sealed at the periphery and junction of the metal rings to form a sealed assembly prior to the diffusion bonding and consolidation process. The sealed assembly is evacuated via at least one pipe and the at least one pipe is sealed before the diffusion bonding and consolidation process.
In these known methods of diffusion bonding and consolidation it is essential that there is a vacuum in the sealed assembly in order to ensure that a satisfactory diffusion bond is formed between the metal rings and that the vacuum is maintained in the sealed assembly when they are subsequently heated and pressed together during the diffusion bonding process.
However, there is a problem using this process because the heat and pressure applied during the diffusion bonding process causes the at least one pipe to collapse/move whereas the metal rings are relatively large and rigid and do not/cannot move at the point of attachment of the at least one pipe. This collapsing/movement of the at least one pipe relative to the metal rings may result in a failure/bursting of the at least one pipe or a failure at the point of attachment of the at least one pipe to the metal rings. The point of attachment of the at least one pipe to the metal rings usually comprises a weld seal and the weld seal may fail during the diffusion bonding process. The failure of the at least one pipe or failure of the weld seal results in a loss of vacuum in the sealed assembly and hence a failure to diffusion bond and consolidate the sealed assembly. This may result in the scrapping of the metal rings and/or metal-coated fibre spirals, which may be high value sub-components.
European patent No. EP0908263B1 discloses a method of manufacturing an article by diffusion bonding in which a pipe is angled relative to an aperture in a sealed assembly to reduce the possibility of failure of the pipe during diffusion bonding.
However, even this arrangement does not fully solve the problem because it is still possible for the pipe to move at its point of attachment, the weld, to the sealed assembly.
Accordingly the present invention seeks to provide a novel method of manufacturing an article by diffusion bonding.